The manufacture of cigarettes and other smoking articles requires the storage of tobacco strip used for the cut tobacco filler for periods of up to 24 months at a moisture content within a desired range. If the tobacco is stored with a high moisture content, i.e., too wet, a preservation problem arises with the possibility that the tobacco will mildew or rot. If the tobacco is stored with a low moisture content, i.e., too dry, it will not age properly, and the resultant product will be subject to excessive breakage during subsequent processing. Typical desired moisture contents are 12.5 percent by weight for flue cured tobacco strip and 13 percent by weight for burley tobacco strip.
Prior to the aging of tobacco during the storage period, the tobacco leaf is cut and formed as a bed or stream on a conveyor system. The conveyor system moves the tobacco stream through various processing stages, including a drying stage, then to a cooling stage where the moisture content is measured, typically by an infrared or near-infrared moisture meter, and then to a reordering stage where the moisture content is finally adjusted to provide the desired moisture content. The drying of the tobacco is performed by blowing air in both updraft and downdraft directions. This results in a compacting or densification of the moving stream of tobacco strip and a slight drying of the tobacco at the upper or exposed surface of the tobacco stream. It is therefore difficult to obtain accurate moisture readings for such a stream of densified tobacco. The standard deviation of moisture content measurement tends to be relatively large and the average moisture content measured by the moisture meter tends to be lower than actual because of the densification and non-uniformity of moisture content from top to bottom of the bed of tobacco strip.
The present invention is directed to overcoming the undesirable effects of measuring the moisture content of a densified stream of tobacco.